<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        /* 伪元素 before,after */
        /* ::selection不能调整字体大小 */
        .box::selection{
            color: red;
            background-color: orange;
        }
    </style>
</head>
<body>
    <div class="box">我是文字,我有很多字,不信你数一数</div>
</body>
</html>